Patent Document 1: JP-A-4-347352
For example, in patent document 1, a reciprocating engine is proposed in which a second piston ring (second ring) disposed with a first piston ring (top ring) interposed between the same and a top surface (head end surface) of a piston is inclined with respect to the reciprocating direction of the piston, such that a gas-pressure receiving area of the piston between the first piston ring and the second piston ring becomes greater on a thrust side than on an anti-thrust side, and gases from a combustion chamber are adapted to be introduced into an annular gas chamber between the first piston ring and the second piston ring. In such a reciprocating engine, larger gas pressure is produced on the thrust side than on the anti-thrust side so as to gas float the piston with respect to the cylinder.